Finding Oswald's dad in Five Nights at Freddy's: Into the Pit means getting access to the most dangerous areas of Freddy Fazbear's Pizza, including the Party Room. To get in, however, you'll need a keycard. If you're stumped on where to find it, here's our handy guide for how to get the Party Room Keycard in FNAF Into the Pit.
After you regain access to the Ball Pit during Night 5 and evade Spring Bonnie after he chases Oswald back into Freddy Fazbear's Pizza, you'll soon realize that a fifth and final child needs to be rescued from the Party Room. This particular room, which we only caught a glimpse of at the very beginning of the game when Spring Bonnie drags his victims into it, is found on the far left end of the Party Hallway.